Find a water container such as a small bucket (plastic or metal), a soda bottle or a milk jug. Get one big enough to contain the amount of water birds use up in one day so you don't have to refill it during the day.
Drill quite a small hole, perhaps 1/8 of an inch, in the lowest part of the bottom of the water container. Fill the container with about 1 cup of water and see if the water drips. If the water drips too slowly for your liking, make the hole bigger.
Drill two 1/8 inch holes in opposite sides of the water container, about 1 to 2 inches from its top.
Cut off the top part of a wire coat hanger, removing the hook and twisted part ; keep the triangular portion.
Thread the wire through the holes near the top of the water container so that about 7 inches of wire comes out on one side of the container. The two sides are not going to be the same length. Bend the two portions of the wire upward and twist them around each other until you run out of the shorter portion. Bend the remaining wire to make a hanging hook.
Fill the water container with water and hang it from a tree branch or shrub so that the water falls into the birdbath. If you don't have a birdbath, place a larger water container such as a garbage can lid, clay pot saucer or wooden barrel underneath the water dripper or mister.